1. Field of the Invention
The present invention relates to an image forming apparatus to which various accessories are attachable. More specifically, the present invention relates to an image forming apparatus that starts a preparation operation in which the image forming apparatus can form an image in response to a start of power supply.
2. Description of the Related Art
Conventionally, some image forming apparatuses, e.g., copying machines and printers, have a power saving mode (sleep mode) function for stopping functions other than predetermined functions for the purpose of saving power. In these image forming apparatuses, it is preferable to reduce the time period for starting up an image forming apparatus when the image forming apparatus returns from the power saving mode to the normal operation mode, i.e., to reduce a user's waiting time.
A method is discussed, in Japanese Patent Application Laid-open No. 11-007343, that data held in a working RAM is moved in a non-volatile RAM when the image forming apparatus enters into the power saving mode, and then, the data saved in the non-volatile RAM returns to the working RAM when the image forming apparatus returns from the power saving mode. Accordingly, the recovery time for the image forming apparatus from the power saving mode can be reduced.
A method is discussed, in Japanese Patent Laid-open No. 2002-354165, that the state of the image forming apparatus entering into the power saving mode is stored in a non-volatile memory when the image forming apparatus enters into the power saving mode, the non-volatile memory is checked when the image forming apparatus is powered on. Then, an initialization sequence is omitted if it is determined that the image forming apparatus is in the state of recovering from the power saving mode.
In the above described circumstances, various accessories, such as a finisher, are connected to the image forming apparatus as optional devices. Accordingly, the image forming apparatus checks types or states of the accessories connected to the image forming apparatus at the time the image forming apparatus is powered on. The image forming apparatus waits for a predetermined time period to determine whether information as to the types or the states of the connected accessories is received from each of the accessories. If the image forming apparatus receives no information from the accessories, the image forming apparatus determines that no accessories are connected thereto. The checking of the types or the states of the accessories is also performed when the image forming apparatus returns from the power saving mode, which may minimize or prevent the reduction of the recovery time required for the image forming apparatus to return from the power saving mode.
A method is discussed, in Japanese Patent Application No. 2006-326861, that the recovery time required for the image forming apparatus to return from the power saving mode is reduced by omitting to check the types of the accessories when the image forming apparatus returns from the power saving mode. In this method, the image forming apparatus is provided with a signal line in order to detect attachment or detachment of the accessories while the image forming apparatus is in the power saving mode, and stores information of the accessories before the image forming apparatus enters into the power saving mode. When attachment or detachment of the accessories is detected while the image forming apparatus is in the power saving mode, the attachment or detachment history is stored. When the image forming apparatus returns from the power saving mode, if the attachment or detachment history while the image forming apparatus is in the power saving mode is not found, the image forming apparatus returns from the power saving mode by using the information of the accessories stored before entering into the power saving mode. In Japanese Patent Application Laid-Open No. 11-005349, a method is discussed that, in a case where status information of each optional unit is stored in an electrically erasable programmable read-only memory (EEPROM) before the image forming apparatus enters into a sleep state and the image forming apparatus returns from the sleep state according to an easy start-up process, the image forming apparatus starts a printing process by regarding each optional unit as being in the status of the information stored in the EEPROM.
However, in the method as discussed in Japanese Patent Application Laid-Open No. 2006-326861, it is required to provide an additional signal line in order to detect the accessories attached or detached while the image forming apparatus is in the power saving mode, which increases cost. Further, since the above method requires power to monitor the attachment or the detachment of the accessories while the image forming apparatus is in the power saving mode, power saving is disturbed. Still further, in the methods as discussed in Japanese Patent Application Laid-Open Nos. 2006-326861 and 11-005349, states of the accessories or the optional units may change while the image forming apparatus is in the power saving mode or in the sleep state. The states of the accessories may change during the power saving mode, for example, in such a case where a sheet on a sheet discharge tray of a finisher is collected by a user or a case where staples of a stapler are supplied while the image forming apparatus is in the power saving mode. Consequently, it is required to check the types or the states of the accessories when the image forming apparatus returns from the power saving mode.